source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/MetalTeapotNew.hlsl @ 1863

float3 F0;

float4 readCubeMap(samplerCUBE cm, float3 coord)                
{
        float4 color = texCUBElod( cm, float4(coord.xy, - coord.z,0) );
        return color;
}

float readDistanceCubeMap(samplerCUBE dcm, float3 coord)                
{
        float dist = texCUBElod(dcm, float4(coord.xy, - coord.z,0)).a;
        return dist;
}

#define MAX_LIN_ITERATIONCOUNT 40  //80
#define MIN_LIN_ITERATIONCOUNT 20  //60
#define SECANT_ITERATIONCOUNT 2
#define MAX_RAY_DEPTH 5

/*
void linearSearch(  float3 x, float3 R, float3 N, samplerCUBE mp,
                    out float3 p,
                    out float dl,
                    out float dp,
                    out float llp,
                    out float ppp)
{
 float3 Ra = abs(R), xa = abs(x);
 float xm =  max(max(xa.x,xa.y),xa.z);
 float Rm = max(max(Ra.x,Ra.y),Ra.z);
 float a = xm / Rm;
           
 bool undershoot = false, overshoot = false; 
 
 float dt =  length(x / xm - R / Rm) * MAX_LIN_ITERATIONCOUNT;
 dt = max(dt, MIN_LIN_ITERATIONCOUNT);
 dt = 1.0 / dt;
    
 float t = 0.01;//dt;
 float pa;
 bool first = true;
 //Linear iteration
 while(t <= 1.0 && !overshoot)
 {
   dp = a * t / (1 - t);
   p = x + R * dp;
   pa = readDistanceCubeMap(mp, p);
   if(pa > 0)
   {
    ppp = length(p) / pa;
    if(ppp < 1)
    {
      dl = dp;
      llp = ppp;
      undershoot = true;
    }
    else if(undershoot)
      overshoot = true;
   }
   else
     undershoot = false;
   t += dt;  
 }

 if(!overshoot)
  p = float3(0,0,0);
}
*/


void linearSearch(  float3 x, float3 R, float3 N, samplerCUBE mp,
                    out float3 p,
                    out float dl,
                    out float dp,
                    out float llp,
                    out float ppp)
{
 float3 Ra = abs(R), xa = abs(x);
 float xm =  max(max(xa.x,xa.y),xa.z);
 float Rm = max(max(Ra.x,Ra.y),Ra.z);
 float a = xm / Rm;
 
 int shootL = 0, shootP = 0;          
 bool found = false; 
 
 float dt =  length(x / xm - R / Rm) * MAX_LIN_ITERATIONCOUNT;
 dt = max(dt, MIN_LIN_ITERATIONCOUNT);
 dt = 1.0 / dt;
    
 float t = 0.01;//dt;
 float pa;
 
 //Linear iteration
 while(t <= 1.0 && !found)
 {
   dp = a * t / (1 - t);
   p = x + R * dp;
   pa = readDistanceCubeMap(mp, p);
      
   if(pa > 0)
   {
    ppp = length(p) / pa;
    if(ppp < 1)
      shootP = -1;
    else 
      shootP = 1;      
    if(shootL * shootP == -1)
      found = true;
    else
    {
      shootL = shootP;
      dl = dp;
      llp = ppp;
    }
   }
   else
     shootL = 0;
      
   t += dt;  
 }

 if(!found)
  p = float3(0,0,0);
}


void secantSearch(float3 x, float3 R, samplerCUBE mp, 
                       float dl,
                       float dp,
                       float llp,
                       float ppp,
                       out float3 p)
{
  for(int i= 0; i < SECANT_ITERATIONCOUNT; i++)
  {
   float dnew;
   dnew = dl + (dp - dl) * (1 - llp) / (ppp - llp);
   p = x + R * dnew;
   half pppnew = length(p) / readDistanceCubeMap(mp, p);
   if(pppnew < 1)
   {
    llp = pppnew;
    dl = dnew;
   }
   else
   {
    ppp = pppnew;
    dp = dnew;
   }
  }
}

float3 Hit(float3 x, float3 R, float3 N, 
           samplerCUBE mp1,
           samplerCUBE mp2,
           samplerCUBE mp3Color,
           samplerCUBE mp3Dist,
           out float4 Il, out float3 Nl)
{
 float dl1 = 0, dp1, llp1, ppp1;
 float3 p1;
 linearSearch(x, R, N, mp1, p1, dl1, dp1, llp1, ppp1);
 float dl2 = 0, dp2, llp2, ppp2;
 float3 p2;
 linearSearch(x, R, N, mp2, p2, dl2, dp2, llp2, ppp2);
 
 bool valid1 = dot(p1,p1) != 0;
 bool valid2 = dot(p2,p2) != 0;
                
 float dl, dp, llp, ppp;
 float3 p;
 
 if(!valid1 && ! valid2)
 {
    linearSearch(x, R, N, mp3Dist, p, dl, dp, llp, ppp);
    Il.a = 1; 
    secantSearch(x, R, mp3Dist, dl, dp, llp, ppp, p);
    Il.rgb =  Nl.rgb = readCubeMap(mp3Color, p).rgb;  
 }
 else
 {
    if( !valid2 || (valid1 && dp1 < dp2))
    {
     secantSearch(x, R, mp1, dl1, dp1, llp1, ppp1, p1);
     Il.rgb =  Nl.rgb = readCubeMap(mp1, p1).rgb;
     p = p1;
    }
    else
    {
     secantSearch(x, R, mp2, dl2, dp2, llp2, ppp2, p2);
     Il.rgb =  Nl.rgb = readCubeMap(mp2, p2).rgb;
     p = p2;
    }
    Il.a = 0;   
 }
 
 return p;
}

struct VertOut
{
        float3 wPos     : TEXCOORD1;
        float3 cPos     : TEXCOORD3;
        float2 texCoord : TEXCOORD0;
        float3 mNormal  : TEXCOORD2;
        float4 hPos : POSITION;                 
};

VertOut DefaultVS(float4 position : POSITION,                                           
                                float2 texCoord : TEXCOORD0,
                                float3 normal   : NORMAL,
                                uniform float4x4 worldViewProj,
                                uniform float4x4 world,
                                uniform float4x4 worldview,
                                uniform float4x4 worldI )
{
  VertOut OUT;
  OUT.hPos = mul(worldViewProj, position);
  OUT.wPos = mul(world, position).xyz;  
  OUT.cPos = mul(worldview, position).xyz;  
  OUT.mNormal = mul(normal, worldI);  
  //OUT.mNormal = normal;
  OUT.texCoord = texCoord;
  return OUT;
}

float4 SingleReflectionPS(VertOut IN,
                                                        uniform float3 cameraPos,
                                                        uniform samplerCUBE CubeMap : register(s0),
                                                        uniform samplerCUBE DistanceMap : register(s1),
                                                        uniform samplerCUBE NormDistMap1 : register(s2),
                                                        uniform samplerCUBE NormDistMap2 : register(s3),
                                                        uniform float3 lastCenter,
                                                        uniform float refIndex)
{
 float4 Color = float4(1,1,1,1);
                
 float3 N = normalize(IN.mNormal);
 float3 newTexCoord;    
 float3 x = IN.wPos - lastCenter;
 float3 V  = (IN.wPos - cameraPos);
 
 V = normalize(V);

float3 R;          
//if(refIndex > 100.0)
    R = normalize(reflect( V, N));
//else
//{
//      refIndex = 1.0 / refIndex;
//    R = normalize(refract( V, N, refIndex));
//}
                        
 float3 Nl;
 float4 Il;
 float3 l = Hit(x, R, N, NormDistMap1, NormDistMap2, CubeMap, DistanceMap, Il, Nl);
 if(Il.a == 0)
  Il = readCubeMap(CubeMap, l);
  
 return Il;
}


float4 MultipleReflectionPS(VertOut IN,
                                                        uniform float3 cameraPos,
                                                        uniform samplerCUBE CubeMap : register(s0),
                                                        uniform samplerCUBE DistanceMap : register(s1),
                                                        uniform samplerCUBE NormDistMap1 : register(s2),
                                                        uniform samplerCUBE NormDistMap2 : register(s3),
                                                        uniform float3 lastCenter,
                                                        uniform float refIndex)
{
         float4 I = float4(0,0,0,0);
                        
         float3 N = normalize(IN.mNormal);
         float3 x = IN.wPos - lastCenter;
         float3 V  = (IN.wPos - cameraPos);
         
         V = normalize(V);
         float3 l;
         
         int depth = 0;
         while(depth < MAX_RAY_DEPTH)
         {
           float3 R;  
           //  R = normalize(reflect( V, N));     
          
          float ri = refIndex;
          
          if(dot(V,N) > 0)
          {
            ri = 1.0 / ri;
            N = -N;         
          }
          R = refract( V, N, ri);
          if(dot(R,R) == 0) R = reflect( V, -N); 
                                
           float3 Nl;
           float4 Il;
           l = Hit(x, R, N, NormDistMap1, NormDistMap2, CubeMap, DistanceMap, Il, Nl);
           if(Il.a == 0)
           {
                   depth += 1;           
           }
           else
           {
                   I = Il;
                   depth = MAX_RAY_DEPTH;
           }
           x = l;          
           N = normalize(Nl);
           V = R;                  
        }
        /*
        N = normalize(IN.mNormal);
        x = IN.wPos - lastCenter;
        V  = (IN.wPos - cameraPos);
        depth = 0;
        while(depth < MAX_RAY_DEPTH)
         {
           float3 R;  
           R = normalize(reflect( V, N));         
                
           float3 Nl;
           float4 Il;
           l = Hit(x, R, N, NormDistMap1, NormDistMap2, CubeMap, DistanceMap, Il, Nl);
           if(Il.a == 0)
           {
                   depth += 1;           
           }
           else
           {
                   I = Il * 0.2 + I * 0.8;
                   depth = MAX_RAY_DEPTH;
           }
           x = l;          
           N = Nl;
           V = R;   
        }*/
        
        //if(I.a == 0)
      // I = readCubeMap(CubeMap, l);
  
        return I;
}

float4 mainPS(VertOut IN,
                                                        uniform float3 cameraPos,
                                                        uniform samplerCUBE CubeMap : register(s0),
                                                        uniform samplerCUBE DistanceMap : register(s1),
                                                        uniform samplerCUBE NormDistMap1 : register(s2),
                                                        uniform samplerCUBE NormDistMap2 : register(s3),
                                                        uniform float3 lastCenter,
                                                        uniform float SingleBounce,
                                                        uniform float refIndex):COLOR
{
        float4 Color = 1.0;
        if(SingleBounce == 1)
         Color = SingleReflectionPS(IN,cameraPos, CubeMap, DistanceMap, NormDistMap1,NormDistMap2,lastCenter,refIndex);
        else
         Color = MultipleReflectionPS(IN,cameraPos, CubeMap, DistanceMap, NormDistMap1,NormDistMap2,lastCenter,refIndex);
         
        return Color;
}